The present invention relates to a chip inductor used in electronic appliances, communication appliances, and others, and its manufacturing method.
In FIG. 6 to FIG. 9, a conventional chip inductor comprises a square columnar main body 21 made of an insulating material, a coil unit 25 having a linear conductor 23 and a groove 24 formed by spirally grooving a conductor layer 22 on the surface of the main body 21, an exterior unit 29 made of an insulating resin 28 applied on the surface of the coil unit 25, and an electrode unit 26 provided at the end portion of the main body 21.
Its manufacturing method comprises a first step of forming a conductor layer 22 on a square columnar main body 21 made of an insulating material, a second step of forming a coil unit 25 having a linear conductor 23 and a groove 24 by grooving the conductor layer 22 by laser 27, a third step of forming electrode units 26 at both ends of the coil unit 25, and a fourth step of forming an exterior unit 29 by coating the coil unit 25 with an insulating resin 28 and drying.
Herein, at the fourth step, while rotating the main body 21 forming the coil unit 25 in the direction of arrow A in FIG. 9(c), on the tape to which the insulating resin 28 is adhered, the insulating resin 28 is applied on the coil unit 25, and the entire circumference of the coil unit 25 is coated with the insulating resin 28.
By drying this insulating resin 28, the exterior unit 29 is formed.
In such conventional constitution, the insulating resin 28 is applied on the surface of the coil unit 25, but the insulating resin 28 was not applied in the inner part of the groove 24 of the coil unit 25.
Generally, in a very small part such as chip inductor (overall dimension being about 1 mm), the interval of adjacent linear conductors 23 in the coil unit 25 is as narrow as scores of microns, and it is hard to coat the insulating resin 28 due to effects of surface tension and others of the insulating resin 28, and coated portions and uncoated portions of the insulating resin 28 coexisted inside the groove 24.
As a result, gaps 40 were formed inside the groove 24 as shown in FIG. 7, and due to air or moisture in the gaps 40, appropriate insulation is not provided between the adjacent linear conductors 23 of the coil unit 25, and short-circuit is caused.
Also in the conventional method, since the insulating region 28 is applied on the coil unit 25 while rotating the main body 21 forming the coil unit 25 on the tape to which the insulating resin 28 is adhered, as shown in FIG. 8, the insulating resin 28 applied on the coil unit 25 forms a circular profile, while surrounding the square columnar main body 21 due to the surface tension.
As a result, the mounting surface by the exterior unit 29 is round, and when mounting a packed substrate or the like, accurate mounting is difficult, and gaps 40 are likely to be formed in the groove 24.
It is hence an object of the invention to present a chip inductor capable of preventing short-circuit and enhancing the electric characteristics by applying an appropriate insulation between adjacent linear conductors of the coil unit, and mounting appropriately by forming a flat mounting surface in the exterior unit, and its manufacturing method.
To achieve the object, the invention is characterized by a constitution comprising a square columnar main body made of an insulating material, electrode units disposed at both sides of the main body, a coil unit connected to the electrode units, and disposed on the outer circumference of the main body between the electrode units, and an exterior unit having the coil unit coated with an insulating resin, in which the coil unit has linear conductors and grooves formed by grooving the conductor layer applied on the surface of the main body, and the insulating resin is also provided in the entire inside of the grooves.
Its manufacturing method comprises a first step of forming a conductor layer on a square columnar main body made of an insulating material, a second step of forming a coil unit having linear conductors and grooves by grooving the conductor layer, a third step of forming electrode units at both ends of the coil unit, and a fourth step of forming an exterior unit by coating the coil unit with an insulating resin and drying, in which the fourth step is intended to form the exterior unit by first coating the coil unit formed on one side of the main body with an insulating resin and drying, then coating the coil unit formed on other side with an insulating resin and drying.
In this constitution, since the insulating resin is provided also in the entire inside of the groove, there is no gap in the groove, and air or moisture is forced out, and appropriate insulation can be applied between linear conductors, so that short-circuit can be prevented.
Also, in this method, in the coil unit formed on the surface to which the main body is adjacent, the insulating resin is applied and dried on the coil unit formed at one side, and then the insulating resin is applied and dried on the coil formed at other side, thereby forming the exterior unit. In this case, the insulating resins applied on the coil units at the adjacent sides are not formed in a circular external shape due to mutual effects of surface tension because one side is already cured. Moreover, since the area of applying and drying the insulating resin in one step is small, the surface tension is smaller, and the insulating resin is easily applied in the entire inside of the groove.
As a result, in the square columnar main body, the insulating resin is also applied in a square columnar form, and an exterior unit of square columnar form is fabricated, and the mounting surface on the exterior unit is flat, and mounting on packed substrate or the like is improved, and the insulating resin may be easily applied to the entire inside of the groove of the coil unit.